Fuel injection plugs for Diesel engines are commonly screwed into the cylinder block. The plugs are formed with a flange or a shoulder which engages a matching shoulder or offset in the cylinder block. It has previously been proposed to provide a heat protecting sleeve which is supported with a flange on a shoulder of the support element, typically the cylinder block, of the fuel injection plug, and which clamps a heat protective ring between the plug and a ring-shaped sealing lip on the sleeve. The heat protective ring is necessary for proper operation of the entire assembly, and particularly for the sleeve.
It has also been proposed to provide heat protection for fuel injection plugs by locating a heat protecting disk with a ring-shaped sealing lip instead of the sleeve or bushing. The bottom of the plug engages the sealing lip and a clamping nut holds the protective disk pressed against a shoulder of the holder for the plug, for example the cylinder block.